Polarized relay



Aug. 15, 1944. E. DICKTEN, JR

. POLARIZED RELAY Filed July 11, 1940 2 Sheets-Sheet 1 FIG! //v VENTORBy E. D/CKTE/V, JR.-

A TTOR/VE 1 Aug. 15, 1944.

E. DIC KTEN, m

POLARIZED RELAY 2 Shets-Sheet 2 Filed July 11, 1940 lNl ENTORE.D/CK7'EN,JR.'

' ATTORNEY Patented Aug. 15, 1944 POLARIZED RELAY Emil Dickten, J12,Totowa, N. 5., assignor to Bell Telephone Laboratories, Incorporated,New York, N. Y., a corporation of New York Application July 11, 1940,Serial No. 34 L893 4 Claims.

This invention relates to an electromagnetic device and moreparticularly to a polarized relay.

It is often desirable in signaling systems to selectively close two workcircuits by the operation of a polarized relay in response to theenergization of its winding by current of either positive or negativepolarity. If a polarized relay of the type which has a single armaturebiased to a neutral position is used for this type of service, there isalways the possibility that if the armature is not accurately biased inthe neutral position, it may fail to operate on current of one polarityor may operate falsely due to vibration when the winding is notenergized or is energized with a non-operating value of current.

It is therefore the object of the [present invention to provide a relaystructure of the polarized type which has three Very definite positionsof which two are circuit closing and the third a neutral or open circuitposition.

.t is a further object of the invention to provide a polarized relaystructure which has a suitable margin of safety against false operationwhen a high percentage of the operate current is flowing and the relayis at the same time subjected to vibrations.

It is also a further object of the invention to provide a polarizedrelay structure which is economical to manufacture and which requires aminimum of maintenance.

In accordance with this invention, several modifications of which haveoeen disclose-d, these objects have been obtained by the use of thenon-linear magnetic characteristic of a section of iron as a magneticrectifier to admit or impede the flow of magnetic flux according to itspolarity. As illustrative, the iron is in the form of a small U-shapedkeeper or yoke shortcircuiting a short permanent bar magnet. A highmagnetic flux exists in the yoke which is considered to be essentiallysaturated. Flux from the core of an elctromagnet is fed into the base ofthe keeper and is directed to either one of two working gaps near theends of the legs of the keeper. In one leg of the keeper, flux due tothe electromagnet opposes the saturating flux set up by the bar magnet,making the sum of the two fluxes less than the saturating value andconsequently operating flux reaches the working gap near the end of thatleg. In the other leg the electromagnetic flux is in a direction to aidthe saturating flux thereby tending to create a flux greater than thesaturating flux but since this can produce only a negligible increase,operating flux can reach only one working gap depending on the directionof the operating current.

lwo independent armatures may be used at the two working gaps or asingle armature may be provided for cooperation with both gaps.

For a more comprehensive understanding of the invention, reference maybe had to the following detailed description taken in connection withthe accompanying drawings, in which:

Fig. 1 is a top plan view of a two armature relay embodying theinvention;

Fig. 2 is a perspective View of a modified form of the invention asapplied to a relay of the sealed switch or contact type;

Fig. 3 shows in cross-section, a mercury type switch element applicableto the relay disclosed in Fig. 2;

Fig. 4 shows in cross-section a magnetic type switch element applicableto the relay disclosed in Fig. 2; and

Fig. 5 is a perspective view of a further modified form of the inventionhaving a single threeposition armature.

Referring first to Fig. 1, the invention has been disclosed as appliedto a well-known type of relay structure, having a core I, the rear endof which terminates in a flattened portion 2 provided with twooppositely extending ears 3 and 4 by means of which the relay may besecured to a mounting rack. Surrounding the core is an operating coil 5.Welded or other wise secured by its base to the forward end of the coret, beyond the front spoolhead 29 of the coil 5, is a U-shaped iron yoke6, the legs 1 and 8 of which extend forwardly with their outer or polefaces lying in planes parallel to the flattened portion 2 of the core I.Secured between the ends of the legs of the yoke K5 is a short permanentbar magnet 9 having its north pole in engagement with the inner face ofthe leg 8 and having its south pole in engagement with the inner face ofthe leg 1. The yoke 6 serves as a keeper for the magnet 9 and is soproportioned that it is normally essentially saturated by the fluxflowing therethrough from the magnet 9.

Disposed on the opposite faces of the flattened portion 2 of the core Iare two U-shaped members iii and it having their bases suitably securedthereto as by screws (not shown) and each having the ends of itsoutwardly extending arms bent oppositely and parallel to the faces ofthe portion 2 to serve as supports for spring pile-ups and for the reedhinges I2 and I3 of the armatures I 4 and I5. Each armature issubstantially U-shaped, the ends of its rearwardly extending legs beinghinged to the forward edges of the members III or I I by the reed hingesand its forward cross-reach overlying an outer pole face of the yoke 6.For adjusting the length of the air gaps between the cross-reaches ofthe armatures and the pole faces of the yoke 6 and for limiting theextent of the movement of the armatures, back-stop studs I5 are securedto the ends of the legs of yoke 6 with back-stop nuts I'I threadedthereon against which the ends of the armatures are normally biased bythe contact springs I8 and 2| which engage against the insulating studs24 carried by the armatures.

Each of the four spring pile-ups, of which two are disclosed, comprisesthree contact springs and two of the spring pile-ups also includeterminal lugs for the coil 5. For example, the lefthand pile-upcomprises contact springs I8 and I9 mounted on the inner face of the armof member I i) and contact spring 20 and terminal lug 25 mounted on theouter face of the arm of member Iil. These springs and the terminal lugare secured to the member II] by screws 26 which extend through holes inthe clamping plate 21, the springs and terminal lug, the member I andinto tapped holes in the inner clamping plate 28. The springs and theterminal lug are insulated from the clamping plates, from the member IDand from each other by interposed strips of insulating material and fromthe screws 25 by the usual sleeves of insulating material which surroundthe screws. The contact springs I9 and 26 are provided with the usualtangs which engage in notches in the front spoolhead 29 for determiningthe gaps between their contacts and the contacts of spring I8. Thepileup including contact springs 2I, 22 and 23 and terminal lug 30 aresimilarly insulatedly supported on the end of member I I by the clampingplates 3I and 32 and the screws 33. The back contact springs 20 and 23may, if not required, be omitted.

Can cover guides 34 are secured at their rear ends to the members 90 andH by the same screws which secure the members to the flattened portion 2of the core with their forward ends engaged against the edges of thefront spoolhead 29.

Considering the operation of this relay, the permanent magnet 9 and theyoke 6 are so proportioned that a flux density is normally produced inthe yoke, sufficiently large to operate the iron of the yoke in thevicinity of or above the knee of the saturation curve. In this high fluxdensity condition the yoke will still have a low reluctance comparedwith that of the air-gaps between the pole faces of the yoke and thecrossreaches of the armatures I4 and I and thus the yoke 6 sufiicientlyshields the armatures magnetically so that there is a negligible initialattractive forc applied to the armatures due to leakage or stray fluxfrom the permanent magnet 8. Neglecting leakage, the permanent magnetfiux may be visualized as leaving the north pole and proceeding aroundthe short-circuiting yoke 6 and entering the magnet at its south pole.

When the coil 5 is energized, a coil flux will be created which willflow through the core I, dividing at its junction with the yoke 6 andwill tend to flow through the legs I and 8 of the yoke, thence acrossthe air-gaps and through the armatures I4 and I5 and uniting again atthe rear end of the core. The direction of the flow of flux in thisdivided flux path will, of course, depend upon the direction of theenergizing current flowing through the coil 5. If the direction of fluxdue to current in the coil is visualized as leaving the core andentering the yoke, the coil flux opposes the permanent magnet flux inthe direction of the armature I5 and the flux density in the leg 8 ofthe yoke is therefore decreased and flux readily flows across theair-gap from the leg 8 to the armature I5, whereby the armature I5 isattracted to close the contacts of springs 2| and 22 and to open thecontacts between springs 22 and 23. At the same time in the leg 1 of theyoke, the coil flux aids the permanent magnet flux but since this leg isalready almost or entirely saturated due to the permanent magnet flux,the increase in flux in this leg will be slight 0r nil and armature I4will be unaffected. Thus armature I5 will tend to operate while armatureI4 remains unoperated.

As the total amount of flux due to the coil 5 approaches that due to thepermanent magnet 9, the entire flux will flow through the leg I of theyoke, through the permanent magnet 9, across the air-gap between the leg8 and armature I5 through the armature back to the core I. This is underthe assumption that there is no leakage flux and that the leg I of theyoke on the side of the unoperated armature I4 can carry no more thanthe initial permanent magnet flux. A current of opposite polarity in thecoil 5 will reverse the direction of the coil flux and cause theattraction of armature I4 while armature I5 is unaffected.

It will be noted that the working flux is due to the current passedthrough the operating coil and the performance is similar to two neutralrelays having oppositely poled rectifiers in series with their coils.The function of the permanent magnet 9 is that of a magnetic rectifier,directing working flux to either one of the armature air-gaps dependingupon the polarity of the operating current. The sensitivity is thuscomparable to that of a neutral relay, the pull on an armature beingproportional to the square of the flux in the working gap due to thecurrent in the coil.

In the unoperated condition because of the permanent magnet flux in theyoke, there is a magnetomotive force drop across it. This tends to sendflux through the path including both armatures and their air-gaps and toproduce some initial force on the armatures. Since the reluctance of theair-gaps is high compared to that of the yoke, even when it is operatedat a high density, this flux and hence the initial steady pull on thearmatures will be small. This will be true so long as the armaturesremain unoperated and the air-gaps are large. When an armature isoperated, however, the reluctance of the correspondin air-gap is reducedand, being in parallel with one of the legs of the yoke, it will drawappreciable flux. Thus, the permanent magnet flux through this armaturecan be made to lock it in the operated position against the back forceof the contact springs operated thereby after it has been brought tothis position by the operating coil. This locking feature can be easilyavoided by the use of armature stop discs of non-magnetic material toprevent too great a reduction of the air-gap reluctance when an armatureoperates.

Fig. 2 illustrates a further application of the magnetic rectifierprinciple to a relay of the sealed contact type. This relay comprises asupporting member or heel piece having a rear upturned car 36 by whichthe relay may be sup ported on a relay mounting rack and two cars 31upturned from the rear edges of the member 35 for supporting pile-ups ofterminal lugs. Each pile-up comprises three T--shaped lugs 38 whichserve as terminals to which the terminals of the operating coil 39 andthe terminals of the switch elements 40 and 4| may be connected. Theterminal lugs of these pile-ups are secured to the outer faces of theears 3? by screws 42 which extend through holes in the clamping plate43, in the lugs 38 and into threaded holes in the ears 3?, the lugsbeing insulated from the cars 31, from the plates 43 and from each otherby interposed strips of insulating material and further insulated fromthe screws 22 by the usual sleeves of insulating material which surroundthe screws.

The forward end of the supporting member is widened out to form a lowerpole-piece 35. Supported on the member 35 intermediate its ends is avertically extending core on which the coil 30 is positioned and on theupper end of which the member 45 is secured. The member 45 and core maybe secured to the member 35 by the screw 45. Secured by its base to theoutwardly extending end of member dii by screws is an iron yoke 41, thedownwardly extending legs 63 and 49 of which are bent outwardly at rightangles to form two upper pole-pieces 5!) and 5! which lie in a planeparallel to the plane of the lower pole-piece M. For maintaining thepole-pieces 50 and 5! properly spaced from the pole-piece 44 and to lendrigidity to the polepieces, a brace 52 of non-magnetic material isinterposed between the member 35 and 45. The upper end of the brace isprovided with lugs engaged between the shoulders 54 of the member 55and. the rear edge of the yoke il and the lower end of the brace isprovided with lugs 55 which engage in notches in the edges of the member355 for holding the brace in its assembled position. Suitably securedbetween the legs 4% and 49 of the yoke M is a permanent bar magnet 55.The yoke i-l' serves as a keeper for magnet 56 and is so proportionedthat it is nor mally practically saturated by the flux flowingtherethrough from the magnet 5%.

The pole-pieces 5d and 52 are provided with two sea-led switch elementsdd and. M.

operable type, two such types suitable for use in the relay structure ofFig. 2 being disclosed in Figs. 3 and 4.

The switch element disclosed in Fig. 3 may be of the type disclosed inthe application of H. C. Harrison and C. E. Pollard, Serial No. 302,526,filed November 2 1939, now Patent No. 2.241493. issued July 1, 1941.This element comprises a tubular glass vessel 5'? into the upper andlower ends of which are sealed the terminals 59 and 58. The lowerportion of the vessel is filled with a p001 of mercury 69 into which theinner end of the lower terminal 58 extends and upon which an annulariron armature 6! floats. The inner end of the upper terminal 59 extendsdownwardly inside of the armature 6! to a point just above the surfaceof the mercury pool. Preferably the vessel 51 is evacuated before it issealed and is refilled with a gas such as hydrogen. If switch elementsof this type are used in the relay assembly of Fig. 2, they are sopositioned in the aligned holes in the pole-pieces thereof that thelower ends of their armatures 6| are positioned above the lowerpole-piece M as disclosed in Fig. 3.

This relay, if provided with switch elements of the type just described,functions in much the same manner as described in connection with theoperation of the relay of Fig. 1 in that normally permanent magnet fluxflows through the yoke 41 and operating flux due to energizing the coilwill tend to flow from the pole-piece 5i! to the pole piece M across theair-gaps between the armature 5i and the pole-pieces to operate thearmature 6i downwardly against the surface tension of the mercury and tothereby displace the mercury upwardly into engagement with the upperterminal 59 to interconnect the terminals 58 and 59 through the mercuryif current flows in one direction through the coil 3% or to cause coilflux to flow from the pole-piece Ad to the pole-piece 3! to similarlyoperate the armature of the switch element 4| to interconnect itsterminals if current flows in the reverse direction through the coil.

The switch elements 45 and ll may be of the type disclosed in theapplication, Serial No. 198,629 of W. B. Ellwood, filed March 29, 1938,now Patent No. 2,289,830, issued July 14, 1942. This switch element,disclosed in Fig. 4, comprises a glass vessel 6'2 into the upper andlower ends of which are sealed terminals 64 and 63 to the inner ends ofwhich are welded reeds 66 and S5 of magnetic material. The overlappingends of these reeds are normally out of engagement and may be providedwith contact surfaces of any suitable metal having good electricalconductivity. The vessel is evacuated before it is sealed and isrefilled with a gas such as helium. If switch elements of this type areused in the relay assembly of Fig. 2, they are so positioned in alignedholes in the pole-pieces thereof that the gaps between the ends of thereeds 65 and 555 are central. located with respect to the upper andlower pole-pieces as disclosed in Fig. 4.

H flow from the pole-piece 59 to the pole-piece M across the air-gapbetween the reed E55 and pole-- piece 58 across the air-gap betweenreeds 535 and '65 and across the air-gap between the reed t5 and thepole-piece 4t and the reeds will be tracted toward each other intocontact engagement if current flows in one direction through the coil35) or to cause flux to flow from polopiece 55 to the pole-piece M tosim larly operate the reeds of the switch element M into engagement ifcurrent flows the reverse direction through the coil.

5 discloses the magnetic rectifier principle app-lied to a relaystructure has g a single armature. In accordance with this modification.a heel-piece 6'! is provided by means of which th relay be secured. to amounting rack. A core d8 extends forwardly at ri ht angle from thheel-piece having a coil 59 thereon and hav ing an iron yoke 1E5 se uredits base to the forward end of the core beyond the front spoolhead ofthe coil 59. The legs H and '52 of the yoke extend upwardly to a mintabove the coil 59 and are provided on their inside surfaces with poleblocks l3 and M welded or otherwise secured thereto. ecured between thelegs TI and T2 of the yoke is a permanent bar magnet 15. The yoke servesas a keeper for the permanent magnet and is so proportioned that it isnormally essentially saturated by the flux flowing therethrough from themagnet.

The heeliece 81 is provided with a tongue 16 extending forwardly overthe top of the coil 69 which serves as a support for two spring pileupsand for the reed hinge 1! of the armature 18. One spring pile-up,comprising the contact springs 19 and 80 and the coil terminal lug 8!,is secured on one face of the tongue 18 by screws 82 and clamping plate83, the springs and terminal lug being insulated from each other, fromthe tongue 16 and from the clamping plate 83 by interposed strips ofinsulating material and insulated. from the screws 82 by the usualsleeves of insulating material which surround the screws. The otherspring pile-up comprising the contact springs 84 and 85 and the coilterminal lug 86 are similarly secured on the other face of the tongue16. The pairs of contact springs 79 and 83, and 84 and 85 normally havetheir contacts out of engagement. The armature '18 is hinged at its rearend by reed spring H to the tongue 16 of the heel-piece 67 and has itsforward or free end positioned between the pole blocks 13 and M. The endof the armature is held in a neutral or mid-position between the facesof the pole blocks by the inside springs 88 and 54 which are biasedagainst the ends of the stud 8? of insulating material extending throughthe armature.

The operation of this relay is much the same as that of the doublearmature relay cf Fig. 1. The locking characteristic previousl describedis of special importance, however. Some of the permanent magnet fluxwill pass across the ends of the legs H and T2 of the yoke through thepole blocks 13 and 14 and through the end of the armature and will causelocking forces to act on the armature. With the armature biased in themid-position, these locking forces are balanced, the armature is inunstable equilibrium, and the relay has a sensitivity to low coil oroperating currents comparable to that of the usual type of polarizedrelay. On high operating currents, however, the operating flux in thegaps is large compared to the permanent magnet flux in the gaps and therelay assumes the square loss characteristic of a neutral relay.

From the foregoing discussion it will be apparent that a relaystructure, which may take the forms illustrated and described or similarforms, has been devised which permits simple, compact and inexpensivemechanical construction since only a small bar magnet and a small yokeor keeper is required to direct operating flux to either on of twoworking gaps; that a relay structure is provided which produces a pullon the armature which is essentially proportional to the square of theoperating current, thus 1 ermitting easy adjustment when close operateand non-operate requirements must be met and whereby a small change incurrent produces a large change in pull compared with the usualpolarized relay having a pull directly proportional to the operatingcurrent; that a relay structure is provided which is not subject tofalse operation even on excess current and that the provision of apermanent magnet with a keeper produces an ideal magnetic condition inwhich the permanent magnet has no tendency to demagnetize and thusdestroy the efficiency of the relay.

While permanent magnets have been disclosed bridged across the legs ofthe yokes 6, 41 and 10 of the relays disclosed in Figs. 1, 2 and 5, itis to be observed that such magnets could be replaced by electromagnetsso designed as to supply saturating flux to the yokes.

What is claimed is:

1. In a magnetic structure, a heel-piece, a core secured thereto, aU-shaped member made wholly of magnetic material secured by its basedirectly to one end of said core, a permanent bar magnet interconnectingthe legs of said member and wholly within the boundaries of said member,two armatures hinged to said heel-piece with their free ends incooperative relationship with the two legs of said member respectively,back stops for adjusting the normal air-gaps between said armatures andthe pole faces of said legs. springs supported by said heel-piece andassociated respectively with said armatures, serving to normallymaintain said armatures against their back stops and a coil on said coreenergizable to cause the selective operation of said armatures dependentupon the polarity of current applied to said coil.

2. In a magnetic structure, a core, an electromagnetic member connectedto said core, a pair of armatures, each of which forms an operatingmagnetic circuit with said core and electromagnetic member, a coil onsaid core energizable by current in either direction for producing anoperating flux in said core, and a permanent magnet forming a closedmagnetic circuit with said electromagnetic member and serving tomaintain said member in a state of substantial saturation for thepurpose of directing the operating flux in said core to one or the otherof said armatures to cause the selective operation thereof in accordancewith the direction of current flow in said coil.

3. In a magnetic structure, a core, an electromagnetic member connectedto said core, a pair of armatures, each of which forms an operatingmangetic circuit with said core and electromagnetic member, a coil onsaid core energizable by current in either direction for producing anoperating flux in said core, and a permanent bar magnet forming a closedmagnetic circuit with said electromagnetic member and serving tomaintain said member in a state of substantial saturation for thepurpose of directing operating flux in said core to one or the other ofsaid armatures to cause the selective operation thereof in accordancewith the direction of current flow in said coil.

4. In a magnetic structure, a core, an electromagnetic memher connectedto said core, an armature forming an operating magnetic circuit withsaid core and electromagnetic member, a coil on said core energizable bycurrent in either direction for producing an operating flux in said coreand a permanent magnet forming a closed magnetic circuit with saidelectromagnetic member and serving to maintain said member in a state ofsubstantial saturation for the purpose of directing the operating fluxin said core to said armature to cause the operation thereof in.accordance with the direction of current flow in said coil,

EMIL DICKTEN, JR.

